how do i report someone for elo boosting an account?

if you played with them hopefully you reported them as unskilled and explained it in the comments. if you want to send in a support ticket you go to the support site and submit a request. idk if the topic matters too much because they will eventually redirect the problem to the correlating team

they would just redirect it anyway to the right people.

There are companies that do this. So it is hard to get them all.
If you find out someone is doing this than the support report is all you have right now

i have seen accounts that where BOT leveled removed quickly and also i have seen them still active after two years.
it will depend on the person who is reviewing the case on how quickly the punishment will be handed out.

if ever

When I sent a support ticket yesterday reporting a booster, for the category, I went with Game and Features > General Questions.

I got a response later that evening that the user in question was being investigated.